Modeling of Series Resonant Dual Active Bridge Converter for DC Microgrid Application

A generalized average model of a Series Resonant Dual Active Bridge (SRDAB) converter with variable phase shift control is proposed in this paper. The transformer current in SRDAB is sinusoidal, so the requirement of negligible ripple current for the conventional averaging technique is not satisfied here. This proposed model uses the output filter capacitor voltage, resonant capacitor voltage, and resonant inductor current as state variables. The dc component and the fundamental component of state variables are used to develop the proposed model. The transformer's leakage resistance is considered for more accurate modeling. With the help of the model proposed, the average model and the small-signal model of the converter are derived and verified using simulation results. The beat frequency dynamics often seen in the resonant converters could be predicted using this proposed model. The analytical expression for small signal control to output transfer function for phase shift control is derived, which aids in the control loop design.